Mechanical pencil



Nov. 14, 1944. B. D. sMn'H MECHANICAL PENCIL Filed March .23, 1943 2 Sheets-Sheet 1 NOV. 14, 1944. l B' D SMH-H MECHANICAL PENCIL 2 Sheets-Sheet 2 Filed March 23 1943 Patented Nov. 14, 1944 MECHANICAL PENCIL Blanchard D. Smith, Atlanta, Ga., assignor to Scripto Manufacturing Company, Atlanta, Ga., a corporation of Georgia Application; March 23, 1943, Serial N0. 480,222

(Cl. 12o-18) 6 Claims.

The invention relates to pencils of the type commonly called mechanical, having provision for feeding lead outwardly or inwardly and to expel the remnant oi the lead from the clutch.

It is an object of the invention to provide a pencil of this character adapted to be made very largely of plastic.

It is a further object of the invention to simplify the lead-expelling mechanism.

Further objects of the invention will appear from the following description when read in connection with the accompanying drawings showing an illustrative embodiment of the invention, and

wherein:

Figure 1 is a side elevation;

Fig. 2 is a side elevation upon an enlarged scale with portions broken away to show the interior and broken out to shorten the showing;

Fig. 3 is a central vertical section with parts about to expel the lead;

Figs. 4, 5, and 6 are transverse sections upon the corresponding section lines of Figure 2 upon a still further enlarged scale;

Figs. '1, 8, and 9 are detail perspective views of the parts of the lead-feeding and expelling mechanism.

As shown the device comprises an external barrel I having internal screw threads as at II, which screw threads, as indicated in Figure 5, are desirably formed as a multithreaded screw shown vas consisting of four threads. Revolubly mounted in the barrel I0 there is shown a slotted tube I2. the form of the slot I3 therein being clearly shown in Figures 4 and 5. The said tube is designed to receive the lead, the end thereof being frlctionally held in the end I4 of the clutch` member I5, shown in perspective in Figure 8.

To propel the lead both in advance and receding movement, there is shown a nut I6 shown in perspective in Figure 9, having male thread elements I1 formed thereon to engage the internal threads II of the barrel I0.

The nut I6, as indicated in Figure 5, is formed complementary to the form of the slot I3 oi the tube I2. Shown as formed separate from the nut I6 there is a rod member I8 seen in perspective in Figure '1, having a head I9 formed to seat within a slot 20 in the nut I6 and to therefore be moved by longitudinal motion of the nut in the slot I3 caused by relative rotation of the barrel and the tube.

The rod I8 is shown as formed with a projection 2| slidable in the clutch I5 and projecting therethrough, as indicated in Figure 6. To normally prevent relative rotation between the clutch I 5 and the tube I 2, the clutch is shown as formed with a projecting member 22, which also normally projects Iinto the slot I3 of the tube I2 contacting the same at the point 23,-Figure 4.

The projection 2| normally projects through the clutch I5 in the opening 24 thereof, which opening is shown as formed with a cam edge for a purpose to be described, and the opposite edge of the slit 1 of the clutch I 5 is formed with a complemental cam edge 26.

The slit 21 in the clutch I5 is shown as of sufiicient width from the cam edge 26 to the point 28 to allow the projection 2| to travel therein. Infthe normal use ofthe pencil the projection 2| of the rod I8 is in axial alignment with the projection 22 of the clutch member and both project into the slot I3 so that `the clutch and rod are prevented from rotation relative to the tube I2. In this position of the parts rotation of thetube I2 causes longitudinal movement of the nut I6 `carrying with it the rod I8 and the clutch I5 thereby producing feeding or retracting motion of the pencil lead indicated at 29, not shown in Figure 4. I

When the travel of the nut brings the clutch and rod to the position shown in Figure 3, the projection 22 of the clutch comes opposite a. cutaway portion 30 of the tube I2 and is therefore not prevented from relative rotation but is prevented from further forward motion by impingement of the end of theclutch tube upon the interior of the barrel IIlat 40. In this condition further outward movement of the nut I6 will cause relative movement between the rod I8 and the clutch I5 causing projection 2| to impinge upon the cam edge 25 which will cause lpartial revolution of the clutch I5 swinging the projection 22 into the cut-away portion 30 of the tube, and continued motion of the nut I6 and the rod I8 will now cause travel of the projection 2| in the enlarged portion 21 of the slit in the clutch I5 causing the rod I8 to pass to the position shown in Figure 2 wherein the remnant of the lead 29 is expelled.

Upon retracting motion of the nut I6, the projection 2| sliding in the slit 21, prevents any rotation of the clutch which wouldV cause clutch lug 22 to leavethe recess 30 of the tube, until the projection 2| contacts the face 26 whereupon the clutch is given a movement of partial rotation, the projection 2| entering the recess 24, and the projection 22 being brought into alignment with the slot of tube I2. This is thenormal working position of the parts and the clutch may now -be retracted to any point and a new To cause motlonof rotation of the tube I2 relative to the barrel, the upper end thereof is shown as formed with a recess 3| which receives a rib 32 upon a cap member 33 which latter is crimped as at 34 into a recess 35 formed in the barrel I0. A ferrule 36 telescoping over the cap 33 is rotatably mounted on the barrel I0, having a' frictional iit with the cylindrical portions of the cap 33. Therefore rotation of the ferrule 36 while the barrel I is held will cause rotation of the tube I2 therein.

As shown the cap 33 is formed with a rib 3| in the tube I2. It will be readily appreciated thatthe rib may be carried by the tube and the recess by the cap with equal facility of operation.

The ferrule 36 is shown as carrying a jacket 31 for an eraser 38.

As clearly shown in Figures 4 and 5 where the sections 1 4 and 5-5 cut through four threads, the threads in the barrel are in the form of multiple screw threads, four being chosen for purposes of illustration. This is an important feature of the invention, particularly when the barrel is constructed of plastic material.

A mechanical pencil, to be acceptable to users, must have a pitch or lead of screw thread of between M; and 1A inch in order to feed the lead at an acceptable rate. The screw threads in the barrel must take the load of thrust resulting from writing pressure on the lead. In order to take this load, the nut must have sufficient bearing surface on the screw threads which can only be secured by a single deep thread or by engaging several tunis of a shallower thread. In the past therefore a deep thread has been used which requires a thermo setting plastic which shrinks less than thermo plastic material but winch is expensive to produce. If the single deep thread be used withvthermo plastic for ejection molding the shrinkage would result in a ridge on the outside oi' the barrel. By use of the small multiple threads of the present invention, the barrel section becomes almost uniform in thickness and the nut may be formed to engage several of the multiple screw threads which may be shallow and yet securethe requiredresistance to thrust. No indication of the small multiple threads on the exterior of the barrel can be seen when the same is formed of a thermo plastic in cheaper ejection molding.

Minor changes may be made in the physical embodiment of the invention within the scope of the appended claims without departing from vthe spirit of the invention.

I claim:

1. A mechanical pencil comprising, in combination: an interiorly threaded barrel; a slotted tube rotatable therein; means to cause relative rotation between the tube and barrel; a lead clutch slidable in said tube having a guide projection slidable in the slot of said tube to normally prevent rotation of the clutch relative thereto; said clutch having an axial slit circumferentially displaced4 from said projection; a lead expelling member slidable in said clutch having a projection carrying thread sections in engagement with 76 the interior threads of said barrel and a projection also slidable in said slot normally in axial alignment with said clutch projection: and means whereby when sliding movement of the clutch is stopped by engagement with the end of the barrel, the member is moved into the slit of the clutch to move therein to expel the lead from the clutch.

2. A mechanical pencil comprising, in combination:` an interiorly threaded barrel the bore thereof adjacent the marking end of the pencil tapering internally to an internal shoulder; a slotted tube rotatable in said bore and having a tapered end with a portion of its wall cut away adjacent said end and near but removed from axial alignment with the slot of the tube to form a recess; a clutch comprising a slitted resilient sleeve slidable in said tube, and formed with a projection to travel in the tube slot, and with a recess from its slit in axial alignment with said projection, the edge of said recess adjacent the projection tapering downwardly and outwardly; a member slidable in said clutch having a portion projecting into engagement with said internal threads and a second portion projecting through said slit into the tube slot, and normally standing in said recess; whereby when the clutch engages said shoulder continued movement of said member swings the clutch projection into said cut away recess, and said second portion into said slit, by continued movement to expel the lead from the clutch.

3. A lead clutch and expelling structure for use with a mechanical pencil having an internally threaded barrel and a slotted tube rotatable therein, said structure'comprising: a sheet of resilient material bent to tubular form with meeting edges; one of said edges cut away to provide a slot, an end of said slot inclined to meet the remaining edge; the remaining edge cut away adjacent the point of such meeting to form a recess opening into said slot with one wall thereof tapering toward the slot; a lead propelling and expelling member comprising a nut portion formed to project into the threads of the barrel,

a rod portion slidable in said clutch and a pro.

jection thereon receivable in said recess and movable into said slot; said rod portion projecting beyond said last named projection a distance greater than the distance between the plain end of the slot and the leadv receiving end of the clutch.

4. A mechanical pencil comprising, in combination: an internally screw threaded barrel member; a longitudinally slotted tube member rotatable in said barrel member; lead controlling means comprising a nut portion having screw thread portions engaging with said internal screw threads and a clutch portion normally actuated by said nut portion; means carried by said nut portion acting to expel lead engaged by said clutch portion upon relative movement between said portions; cam means carried by one of said portions and coacting between said portions to position the same for relative movement, a portion of said clutch portion contacting a part of one of said members in the travel of said portion and thereby preventing such positioning movement by cam action; said contacted part cut away adjacent the end of the forward travel of the clutch portion to permit such positioning movement.

5. A mechanical pencil comprising, in combina` tion; a barrel formed with multiple internal screw threads; a longitudinally slotted tube rotatable in said barrel, lead controlling means slidable ln said tube having a nut means projecting from said slot and formed with a plurality of screw thread portions engaging respectively a plurality of said multiple internal threads whereby to distribute writing thrust among said engaged threads.

6. A mechanical pencil comprising, in combination; a barrel formed with multiple internal screw threads; a longitudinally slotted tube rotatable in said barrel, lead controlling means slidable in said tube having a nut projecting from said slot and formed with a plurality of screw thread portions engaging respectively a plurality oi' said multiple internal threads, a clutch portion conned within said tube and coupled with said nut tor normally gripping the lead.

BLANCHARD D. SMITH. 

